Do you have a source for this? How did it work -- the individual ISPs contacted websites they intended to blacklist and gave them the opportunity to appeal?

I find this hard to believe since Justin Hancock, who runs BishUK, claims to not have been aware that his website was being blocked until Newsnight alerted him.

If you are right, then perhaps he got some kind of form email alerting him of this possibility and assumed it was not relevant to his business?